Liquid piston pumps for dispensing liquid through a countertop from a reservoir disposed below the countertop are known in which the body of the pump is inserted through an opening in the countertop into a reservoir, with merely an actuator and discharge outlet above the countertop. These liquid pumps are operative in a single stroke as to allow the production of a desired unit dosage volume of liquid. The opening through the countertop is selected to be as small as possible, for example, ⅞ inch in diameter, to provide a pleasing appearance.
Foam piston pumps are known for simultaneously dispensing a liquid mixed with air as in a foam. One such foaming pump is disclosed, for example, in U.S. Pat. No. 7,337,930 to Ophardt et al, issued Mar. 4, 2008, the disclosure of which is incorporated herein by reference.
The inventor of the present application has appreciated that previously known foam piston pumps suffer the disadvantage that the pumps typically cannot be inserted through a relatively small opening into a reservoir and have a reasonable stroke length while allowing an adequate volume of air to be displaced as to allow the production of a desired unit dosage volume of foamed liquid product in a single stroke. The present inventor has also appreciated the disadvantage that with known foam piston pumps, as the diameter of the opening through which the pump is to be inserted reduces, then the stroke length required to dispense a desired volume of air increases.